Apparatus for the extraction of cellulosic fibers from vegetable material



Nov. 25, 1941. u PQMILIQ APPARATUS FOR-THE EXTRACTION 0F CELLULQSICFIBERS FROM VEGETABLE MATERIAL Filed July 16, 1937 5 Sheets-Sheet 1 INVE N TOR UMBEETO POMILIO B mww HTTQRNEYS APPARATUS FOR THE EXTRACTIONOF. CELLULOSIC FIBERS FROM VEGETABLE MATERIAL Filed July 16, 1937 5Sheets-Sheet 2 Nov. 25, 1941. u. POMILIO 2,263,903

I N V E N TO R U BER-r0 PaM/uo ATTaENEYS Nov. 25, 1941. u. POMILIO2,263,903

APPARATUS FOR THE EXTRACTION OF CELLULOSIC FIBERS FROM VEGETABLEMATERIAL v Filed July 16, 1957 T 5 Sheets-Sheet 3 I NVE NTOR UMBERTO PomNOV. 25, 1941. u POMILIQ 2,263,903

APPARATUS FOR THE EXTRACTION OF CELLULOSIC FIBERS FROM VEGETABLEMATERIAL Filed July 16, 1937 5 Sheets-Sheet 4 "Nam-oz umgggro POM/L10 8v Md-W Nov. 25, .1941. u. POMILIO 2,

APPARATUS FOR THE EXTRACTION OF CELLULOSIC I FIBERS FROM VEGETABLEMATERIAL Filed July 16, 1937 5 Sheets-Shgt 5 I 1 Ii v 0 INVcNro'R fUAfIdERTo FBI-114.1:

AQQM firmer/5Y5 Patented Nov. 25, 1941 APPARATUS FoR THE EXTRACTION FCELLULOSIC FIBERS FROM VEGETABLE MATERIAL 1 Umberto Pomilio, Rome,Italy, assignor to Pomilio 2,263,903 I C E Corporation Limited, London,England Application July 16, 1937, Serial No. 153,993 In Great BritainAugust 15, 1936 3 Claims.

The invention is for improvements in or relating to apparatus for theextraction of cellulosic fibers from vegetable material and particularlyfrom vegetable material such as the stalks of the velocity at which thereactions take place and the rate at which the heat evolved isdissipated through the mass of the material and through the walls of thereaction vessels. The velocity at which the reaction takes place in thealkali wheat. barley, oats, rice and other cereals, and 5 treatment isdependent on the amount of alkali of flax, maize, cotton, hemp, and frommaterial emcriiltoryedtfor aflgiverihweiglliitlof materialtreated suchas sisal, phormium tenax, bagasse, different an e s reng 0 e a a 1 so uion.

grasses such as esparto, tow-residues and A feature of the inventionconsists in emp yresidues from the manufacture of textile matein e a iin q ah eS only j s fll t t rials. One of the objects of the inventionis to react with and/or dissolve the encrustmg subproduce cellulosicfibers suitable for the manustances referrvlelii to abo there s ot befacture of high-grade and other forms of paper an xcess of a a andcardboard and the like The c ll l io A further feature of the inventionconsists in fibers which are present in the materials set out employinga alkali lu 6 a Caustic soda above are for the most patrtdembtelllidedin ligneous i gilg 213111 1237 8? zgf r g-tivwlgigpilfiigss S8; or woo ymater encrus e wi waxes, resins, 1 n is e ectic, mucic nd albuminousmatter d mi the reacting substances are selected to be one eralcompounds (e. g. silica compounds). It is p y Weight o e able te ial tof0ur to already known how to extract the cellulosic fibers SIX pa s ofthe so utio :I'he reaction 1s carried by dissolving out the abovementioned substances 2 out 1n an open vessel without p e su e for a byeating the li mate t t i i S21E21 if?Th2;Jiitflfitfifififlitt E; 312 andchlorine. The a all removes a su s an ia part of the encrusting b twhile t solution, the extent of the mitial dlsmtegratlon chlorine reactswith the ligneous of woody matof t material a i th r tu y va y t-er. Theconcentration of the alkali solution 25 fIOm usually t been g i is 21SZZxfiifiitii is iiffiit 3552352??? amounting 0 107 or hig er, and sim ary, where chlorine has been used, it has been em- 3 3 21 9 5 l g ig fi gi ployed in an undiluted state. Paper manufac- 6 1g 6 m 9 6 5a 6 metured from the resulting fibers has tended to be 30 g g a e g y ge harshand crackly. 0

It has now been f d that inter alia the fibers, in addition to beingadversely affected by temperature under which the alkali reaction of ggt ggg fig i gfi z gg igig i wgl g the above treatment is carried outafiects the 1 of e fiber strength thirtieth a tars: that hightemperature COIldltlglgS tend to damage takes place and the at Whicr theheat s the fiber, for example the fi r is increasingy damaged with theincrease of temperature over fz i gi gfig gt giif g fg ig and ggg g ggg22 E221 i figggifi: and mgh 40 An important feature of the presentinvention According to this invention a proce'ss for the consists ineffecting the chlorination treatment of the vegetable material bycausingchlorine gas extraction of cellulosrc fibers fromvegetable madilutedwith air to be conducted through the terial comprises treatmg mammal mterial Preferably the chlorine gas and reacting vessel with an alkalisolution under cond1t1ons mass both moist with water The function forcomplete reaction with substantially all the t t t f th t ted teri 31 toof the air is twofold. It reduces the velocity at an g ter de which thereaction takes place and thus the rate vesse w was e W wa a at whichheat'is evolved, and it also forms a vewaten ng the matenal' treatmg.thew hicle for conducting away the heat. Furtherntatenal another open Wlthc lorme gas more, due to the moisture the resulting hydrodfluted Wlthunder condltlons for complete chloric acid is of such a dilution as tobe less reacmm i substantially? the lignemls F- harmful to thecellulosic fibers than if the chloterr e e the mammal m the last 551drine is dry. The proportion of air used with the Vessel 1m1 ned1ate 1Yupon compktlfm of the chlorine is dependent on the nature of thevegetion and lmmelfismg the matePal m a colfi Water table material beingtreated and it may vary bath, transferrlhg the matfina1 t a Sald h from.5 to 1. part by volume of air to one part to another vessel andtreating it with an alkali by volume of chlorine, while the moisturesolution for dissolving the previously reacted subt t of the chlorinemay be up to its Saturation Y stances. Since the react1ons are exothermie point and the moisture content of the mass may tempe atur s built pare d p nt t a n be two to five times the dry weight of the mass itself.

The rate at which the chlorine-air mixture is passed through thevegetable material also varies with the nature of the material beingtreated,

since certain materials can be treated at higher temperatures thanothers without adversely affecting the cellulosic fibers. For example,wheat straw may be treated up to a temperature of 55 C. while hemp strawmay be treated up to 65 C. The rate at which chlorine may be passedthrough the material per pound of the material per hour varies from of apound to V of a pound. The length of the chlorination treatment may varyfrom half an hour to three hours.

The process according to this invention in-.

volves reactions which are controlled as to concentration of solutions,maximum temperature rise and time of treatment, which reactions arecarried out successively in separate reaction chambers. in reducing to aminimum the time when the fibres are in contact with the hydrochloricacid resulting from the chlorination, for example, the mass is immersedin cold water as soon as the chlorination is complete.

A further aspect of the invention consists in that the vegetablematerial is subjected to a further treatment with alkali after thechlorination treatment. As already indicated, the first alkali treatmentis carried out under conditions which remove a substantial part of theencrusting substances and do not attack the: ligneous matter. Thus, in a881156111118 first reaction is a partial reaction. The chlorinetreatment reacts with the ligneous matter-and forms chloro-ligriinecompounds. These compounds may not be entirely removed by the immersionin water and the function of the second alkali treatment is to dissolveout these chloro-lignine compounds. The strength of the alkali solutionemployed for this latter treatment may be as low as .l%. The quantity ofsolution employed is from 5 to 20 parts by weight of solution to 1 partby weight of vegetable material. As a rough guide the quantity of alkalirequired in the last alkali treatment is less than half that employed inthe first treatment. The temperature at which the reaction takes placemay be up to 100 C., and the length of time of the treatment may be aslow as a few minutes.

The plant employed may embody an apparatus for mixing solid dividedmaterial, such as the aforesaid chopped vegetable material, with areacting liquor, such as the alkali, which appa ratus comprises a hopperor thelike arranged above an elongated mixing chamber having a bottomwall sloping in the direction of the length of the chamber. a conveyorin said chamber arranged to traverse the material from the deep end toan outlet at the shallow end, means for introducing the reacting liquorat a controlled rate to said chamber. By these means the material canbe-arranged to pick upor absorb the desired quantity of liquor duringits passage through the mixing chamber. The mixing chamber may be.provided with two outlets, one at each end thereof, and with an invertedV-shaped bottom wall and said hopper may be disposed above the apex ofthe Vj-shaped bottom wallso that the conveyor is arranged to traversethe material outwardly from said apex to'said out lets. An invertedV-shaped deflector may be disposed above the centre of the conveyor andsaid hopper and means may be provided for ad A feature of the inventionconsists.

aaeaeos to one side or other of the said V-shaped deilector.

The plant may also embody an apparatus for extracting compacted massesof interlaced fibers from the bottom of treating towers or the like,which apparatus comprises a number of parallel or horizontal shaftsspaced apart and having radially extending arms and means for drivingadjacent shafts in. opposite directions. Means may be provided forvarying the distance apart of said shafts.

In an apparatus for the extraction of cellulosic fibers from vegetablematerial by successive alkali and chlorine treatment, means are providedfor converting the material to a fioccular state after the removal ofthe liquor in the alkali treatment and a blower connected with asuitable conduit is provided for conveying by cold air the floccularmaterial in a divided state to the top of the chlorine tower. Areceiving chamber may be arranged over the top of the chlorine towerwhich is provided with a deflecting wall on to which the floccularmaterial is directed by said conduit and is thereby caused to fall intosaid tower.

The following is a description of one form of apparatus for carrying outthe process described above, reference being made-t0 the accompanyingdrawings in which:

Figures 1a and lb taken together represent a side elevation of the plantshowing diagrammatically the general arrangement.

Figure'2 is a vertica'lsection on the line 22 of Figure la showing thealkali towers'in elevation.

Figure 3 is a section through a tower on the line 3-4 of Figure 1.

Figure 4 is an enlarged view of one of the mixing devices of Figure 2.'

iustably directing the material leaving the hopper Figure 5 is anenlarged view ofthe mechanism for tilting the hopper nozzle as shown inFigure 4.

Figure 6 is a side elevation of the device shown in Figure 5. 4

Figure 7 is a plan view of the extractor for the reaction towers.

Figure 8 is an elevation of the arrangement shown in Figure '7.

Figure 9 is a cross section on the line 8-9 of Figure 8.

. Assuming stalks orstraw of plants, such as are referred to at thecommencement of the specification, are to be treated, these are cut intolengths of a few inches and are loaded into hoppers l0 arranged at thetop of the apparatus. The apparatus about to be described is designedfor producing about 15 tons of cellulose per day. Each hopper isarranged to deliver the material to an apparatus II which mixes thestalks with an alkali solution in, the required proportions and deliversthe" mixture to the upper ends of a pair of vertically-arranged reactiontowers l2. Each mixing apparatus thus serves two towers, and comprises along horizontally-disposed chamber "open at the top, the lower wall llof which is inclined downwardly from each end to the centre to form a V.A screweconveyor .15 is horizontally-disposed along-the length of thechamber and has two sets of helical blades arranged end to end, whichblades vare oppositely pitched to one another, and are driven by a motor22. Disposed above the chamber and at the centre of the screwconveyor isa V-shaped deflector I6. The hopper is arranged to deliver the materialon to the deflector through a flexible nozzle I! which may be swung fromone side to the other of the V-shaped aaeaoos deflector therebyadiusting the relative quantitles of the material being fed to the twotowers. The movement of the nozzle may be effected by a hand wheel ll toa worm shaft I! in engagement with a rack 2| secured to the ironic. Thewormshaft is mounted in a bracket 2| secured to the chamber l5. Causticsoda solution is supplied to the chambers through a conduit 23 and asuitable device for maintaining a constant level of the solution in theV-shaped recess in the bottom of the chamber but which level does notreach the blades of the conveyor. As already indicated," the strength ofthe solution may be from 1 to 2%. Each end of the chamber is open andthe screw-conveyor forces the material mixed with the alkali out throughsaid open ends from which mixture drops into the open end of thereaction tower l2. s

The reaction towers may be about 34 feet high and in cross-section areflattened oval-shaped (as will be seen from Figure 3), the smallerdimension being about inches and the larger dimension 8 feet. Theconveyor I 3 is so arranged as to eflect a mixture of straw and solutionin proportions of one of straw to four of the solution. Steam isintroduced through the walls of the tower by a number of pipes 24 in azone substantially above the horizontal centre line, e. g. onequarter ofthe length from the top. The steam generating plant 25 and main deliverypipe 2 are shown to the left of Figure l. The mass of material graduallydescends under gravity and becomes compacted as it descends, and at thebottom forms a seal which prevents too rapid an escape-of the liquid.The time of descent may vary from one to four hours according to thenature of the material and the strength of the caustic solution. Duringthis time the alkali is almost completely used up'to form spent liquorof a dark colour. The tower is provided with inspection windows 9 andsockets 8 for thermometers at different heights.

When the mixture arrives at the bottom of the tower it is in the form ofcompacted interlaced fibers whence it is removed by an extractor ll, thespeed of extraction beingadjustable; thus, the time of treatment may bevaried.

. 42 to an opener 43 having spiked rollers or combs where it isconverted into a floccular state. It is then raised by air blowers 44through suitable conduits 4| to a receiving chamber 4! arranged I abovethe upper end of a set of chlorinating towers 41. The upper ends or thechiorinating tow-- ers are open and the conduits 45 are directed on to adeflecting plate 4. in the collecting chamber 46 whereby the floccularmaterial-is caused to fall into the towers. This treatment results inthe floccular material having a dryness factor of from about 25 to 40,i. e. 75% to 60% water and 25% to 40% bone dry material.

These towers may also be about 30 feet in height although those shown inthedrawings are shorter.'-' They are of a flattened oval shape incross-section, the general dimensions being the same as those of thealkali towers. Chlorine is introduced into the fibrous mass at a zoneabout 10 feet from the top of each tower. As already indicated the topof each tower is open but the 10 foot column of fibrous material abovethe zone is sufllcient'completeiy to absorb the chlorineAswillbeseenfromFigure7to9theextractor'- comprises'two parallel shafts2! each of which can-is a ,number of star-shaped members II. The twoshafts are rotated through gearing 80 in opposite directions so that thearms of the stars draw the material downward and flrst move towards oneanother and then away from one another. The mounting for shafts 28 andthe ing device is formed in two parts 33, 34 arranged. end to end alongthe length of its conveyor and the part at the outlet end 34 receives asupply of wash water through a pipe 38 which wash liquor is delivered byan outlet pipe I to a tank 31. The

washed and partly-treated fibers are delivered by the conveyor throughan outlet conduit ll to a screw-press 39 where the remainder of thespent liquor is squeezed out of them and delivered to a tank 4| througha pipe 4|. The consolidated mass is then passed through a conduit andprevent leakage, and the sealing action is enhanced'by the fact that thematerial is descending". The "chlorine is' introduced into the zone bypipes 48 which extend from a header pipe II through the walls of thetower and'stop flush with the inside face, and also by means of a set ofpipes il which extend downwardly from a header pipe. From practicalconsiderations the width between the side walls of the tower cannot bemade much less than I! inches and since chlorine cannot readilypenetrate the librous material to that extent, the additional verticaldelivery pipes are provided. -'Ihus, a comparativ'ely small penetrationis required without the necessity of applying substantial pressure tothe chlorine. Chlorine with the required degree of moisture may-beprepared in an electrolytic plant 53 from which it passes through adelivery conduit 54 to a blower l5 driven by a motor 56.

The inlet or suction side of the blower communicates with the atmospherethrough a valve 51 and alrpipe ll. 13y adjusting the valve 5! a desiredvquantity of air may be mixed with the chlorine.

tion windows 9 and sockets for thermometers are provided.

The material is then delivered by the extractor into a tank I havingrotating stirrers ll therein through which tank cold water iscirculated. The material passes thence along a trough 62 to a rotatingconical sieve 82, the axis of which is horizontal and the angle ofinclination of the walls of which is such as to feed the material fromthe smaller end of the'sleve to the larger end. The diluted hydrochloricacid percolates out through the sieve walls into a'tank 64 and thefibrous material thus partially freed of acid is passed throughscrew-presses 65 where it is consolidated. The fibrous material is thenpassed through a mixing vat I containing a weak solution of causticsoda, e. g. a soda solution of 2% concentration or less. The material istreated in this vat for a fraction of an hour and this results in theremoval of the chloro-lignine compounds and/or other non-cellulosesoluble matter. Also, any remaining hydrochloric acid or chlorinecombines with the caustic soda. Thereafter the fibers are passed throughthe usual washing and sorting apparatus where knots are removed.

As already indicated the towers both for the alkali and chlorinetreatments are provided with thermometers so that the predeterminedtemperatures of the reactions may be maintained, for example, bycontrolling the rate of extraction of the material from the bottom ofthe towers. Furthermore, means are provided for periodically testing theair and moisture content of the chlorine mixture.

The starting material may be considered to contain roughly 50% celluloseconstituent and 50% non-cellulose constituent. Each of the first twotreatments, 1. e. the first alkali treatment and the chlorine treatment,result each in the removal of about 30% non-cellulose constituent,

' whereas the final alkali. treatment results in the removal of 40% ofthe non-cellulose constituent. The attenuated nature of the treatment ina number of steps and the comparatively slow velocity of the reactionand the comparatively low temperatures under which the reactions arecarried out result in a high yield of fibrous cellulose of good qualityand suitable for the manufacture of a high grade of paper owing to itsstrength, softness and pliability.

The stalks of plants, such as are mentioned at the commencement of thespecification, contain about 8% ligninby weight of the material andabout 42% of waxes, resins, pectic, mucic and albuminous matter, etc.The amount of alkali required for reaction with these latter substancesis about half their weight. The chlorine gas reacts with all the ligninand with certain other non-cellulosic materials. It is important thatthe first alkali treatment should remove only about 30% of thenon-cellulosic encrustants, since their presence in the materialduringthe chlorination treatment insures the formation of chloro-ligninswhich are readily removed by the final alkali treatment. Since only 30%of the encrustants are to be removed by the first alkali treatment, i.e. an amount equal to 15% by weight of the material, and since theencrustants require about half their weight in alkali for the reaction,the weight of alkali required is about 7 by weight of the raw materialor roughly the weight of the raw material.

There remains in the material after the chlorination treatmentchloro-lignin and certain other chlor-organic compounds, together withsome remaining encrustants. The chloro-compounds, however, require verylittle alkali for their dissolution and the total amount of alkalirequired in the last step is less than half that of the first alkalitreatment.

It will be appreciated that many modifications may be made to details ofthe above process and apparatus without departing from the scope of thisinvention.

I claim:

1. An apparatus for extraction of cellulosic fibers from vegetablematerial comprising a mixing chamber having a bottom wall sloping in thedirection of the length of the chamber, means for introducing thevegetable material into said chamber, a conveyor in said chamberarranged to traverse the material from the deep end to an outlet at theshallow end, means for introducing an alkali solution at a controlledrate to said chamber, means for directing the mixture from said outletto the top of a vertical reaction tower open at the top, means forintroducing steam into the upper part of the tower, means for extractingat a controlled rate the treated material from the bottom of the tower,means for removing the liquor from the treated material, a secondvertical reaction tower open at the top, means for introducing thetreated material into the top of the second tower, means for introducingat a controlled rate chlorine diluted with air into the upper part ofthe second tower, means for extracting the chlorinated material at acontrolled rate from the bottom of said tower and for introducing itinto a cold water bath, a vessel containing a weak alkali solution, andmeans for transferring material from the water plant to said vessel.

2. An apparatus for the extraction of cel-,

vegetable material to the central zone of said chamber, a conveyor insaid chamber arranged to traverse material from the centre outwards toan outlet opening at each end of the chamber, means for introducing analkali solution at a controlled rate to said chamber and means fordirecting the mixture from each outlet to a separate vertical reactiontower open at the top, means for introducing steam into the upper partof each tower, means for extracting at a controlled rate the treatedmaterial from the bottom of each tower, means for removing the liquorfrom the treated material, another vertical reaction tower open at thetop, means for introducing the material to the top of the later tower,means for introducing at a controlled ,rate chlorine diluted with airinto the upper part of said latter tower, means for extracting thechlorinated material at a controlled rate from the bottom of said towerand for introducing it into a cold water bath, a vessel containing aweak alkali solution, and means for transferring material from the waterplant to said vessel.

3. An apparatus for the extraction of cellulosic fibers from vegetablematerial, comprising a vertical reaction tower open' at the top, meansfor introducing into the top of the tower the vegetable material mixedwith alkali solu-" tion; means for introducing steam into the upper partof the tower, means for extracting at a controlled rate thetreatedmaterial from the bottom of the tower, means for removing the liquorfrom the treated material, a second vertical reaction tower open at thetop, means for introducing the treated material into the top of thesecond tower, means for introducing at a controlled rate chlorinediluted with air into the upper part of the second tower, means forextracting the chlorinated material at a controlled

